TITLE:   GCN CIRCULAR
NUMBER:  6021
SUBJECT: GRB 070110: optical break
DATE:    07/01/22 20:20:04 GMT
FROM:    Daniele Malesani at Niels Bohr Inst,Dark Cosmology Center  <malesani@astro.ku.dk>

D. Malesani, J.P.U. Fynbo (NBI/Dark), A.O. Jaunsen (Univ. Oslo), and 
P.M. Vreeswijk (ESO), report on behalf of a larger collaboration:

We observed the optical afterglow of GRB 070110 (Krimm et al., GCN 6005) 
with the ESO VLT + FORS1. BVRI photometry was secured around Jan 21.05 
UT (~10.7 days after the GRB).

Afterglow photometry in the V band shows its magnitude to be V ~ 24, 
significantly fainter than expected based on the extrapolation of the 
UVOT decay, which would predict V ~ 22.5 (Krimm et al., GCN 6019; see 
also GCN report 26.3). We also measure the relative decay in the R band 
based on comparison with our previous images (Jaunsen et al., GCN 6010; 
Malesani et al., GCN 6015), and find it steeper than the value reported 
by UVOT in the U, B and V bands.

The above evidence supports a steepening of the optical light curve of 
GRB 070110, which possibly occurred some 5 days after the GRB, the time 
at which the UVOT light curves end.

Further observations are encouraged. We acknowledge excellent support 
from the observing staff at Paranal.